The basic idea is to do this on Sundays, since the time frame will be the most ample to kill the lich.
The strategy here is to take down the lich by luring the Bomb Steeds to it through the skill with play dead. Ideally you can use a character with ~ level 30~45.
One of the thing to make sure is that you have enough experience to revive on spot.
The Trick is that the lich will not spawn more horse until there is only one horse or none left. So it is best to aggro all the horses, and if some horses are left over
you have to make them explode until there's 1 or 0 remaining.
Another trick is to not revive on spot as often. For instance, the horses will not target until they start moving after summon, so if you are dead you can wait until they start moving then get up. In addition, if you are dead and some horse are already about to explode, you can wait until they explode then get up as well.
You will be able to know if the Bomb Steed is about to explode as they will start flashing red.
Here's the Video Guide Using the Skeleton Pet since it have the special ability play dead. (Elves can also use the "hide" ability at times to move around in better position).